DE2332704C3 - Process for the preparation of trimethyl-p-benzoquinone - Google Patents

Description

It is known that trimethyl-p-benzoquinone can easily be reduced to trimethylhydroquinone, the one important starting compound for the production of vitamin E isL

There are various methods of making trimethyl-p-benzoquinone by the oxidation of trimethylphenol known. According to J. Org. Chem. Vol. 4 (1939), p. 318, trimethyl-p-benzoquinone in 5Q percent Yield produced by oxidation of trimethylphenol with chromic acid in aqueous sulfuric acid will. This publication also describes trimethylphenol with a diazonium compound to couple and to hydrogenate the product obtained to form trimethyl-p-aminophenol, the then with iron (III) chloride in 95 percent Yield is oxidized to trimethyl-p-benzoquinone. However, the known methods are economical disadvantageous in that they require numerous steps and expensive chemicals.

According to the Japanese patent publication Mr. J8 063/70, which corresponds to DE-OS! 8 14 652, The process described is trimethyl-p-benzoquinone in a yield of 69.6% of theory thereby prepared by 2,3,6-trimethylphenol in acetic acid dissolves and oxidizes this with dilute nitric acid using sodium nitrite as a catalyst However, the process is not yet completely satisfactory in terms of yield.

Other oxidation processes are known from the literature, but in numerous cases one of them Diphenoquinone homolog is formed and the Selectivity in the formation of trimethyl-p-benzoquinone is low

According to a proposal not previously published, 2,3,5-trimethylquinone can be obtained by oxidation of 4-chloro-23.6-trimethylphenol with oxygen and copper (tl) chloride in dimethylformamide and water.

The object of the invention is to provide a new process for the production of trimethyl-p'benzoquinone create that takes place in high yield and avoids the formation of diphenoquinone homologs will. This object is achieved by the invention

The invention thus relates to a process for the preparation of trimethyl-p-benzoquinone by oxidation of trimethyl-p-halophenols, which thereby is characterized in that the oxidizing agent used is chromic acid, Pennanganic acid, a peroxide, diluted, uses concentrated or fuming nitric acid.

Of the oxidizing agents, nitric acid gives the best results and is the most economical. Dilute, concentrated or fuming nitric acid is therefore preferably used.

Surprisingly, that of the trimethyl-phalogenophenols takes place without induction period, i.e. the oxidation starts immediately after the addition of the oxidizing agent and in the absence of a catalyst. The method according to the invention has the advantage that the trimethyl-p-halophenols used according to the process are easily accessible by halogenation of 23,5- or 23,6-TritnethylphenoI. The hydroxyl group of the phenols used directs the entry of the halogen atom into the ortho and para positions to the hydroxyl group. If you use the halogenation by the process of the invention Carries out low temperature, surprisingly occurs almost exclusively in the halogen atom Para to the hydroxyl group. In particular when using 23,6-trimethylphenol, the Para position quantitatively substituted by the halogen atom, since the ortho positions by methyl groups are substituted. The halogenated trimethylphenol can be used without isolating the halogenation product are oxidized immediately.

μ The halogenation of 23,5- or 23,6-trimethylphenol to produce the 23.5 or 23.6-Trimethyl-p-halophenols is preferably used in carried out with a solvent that can be used for conventional halogenation reactions, such as acetic acid, carbon tetrachloride and carbon disulfide. However, it can also be any other Solvents are used, provided that it dissolves the trimethylphenol used, and not on the

η halogenation reaction takes part With regard to the subsequent oxidation, carbon tetrachloride is called

Solvent particularly preferred because this is Can easily be separated again solvent Chlorine, bromine or iodine can be used as the halogenation agent

j5 can be used. Chlorine is preferred for economic reasons. The halogenation is preferably carried out at temperatures of 0 to 10O ⁰ C, in particular at 20 to 80 ° C carried out usually the halogenation proceeds quantitatively in the absence of KaIatysators. To improve the selectivity of the halogenation in the para position, however, iron powder, sodium acetate or a Friedel-Crafts catalyst such as aluminum chloride or iron chloride can be used. The addition is particularly preferably less

Amounts of iodine in chlorination or bromination.

The oxidation is preferably carried out in a solvent, such as water, acetic acid, an aliphatic hydrocarbon such as hexane or heptane, a halogenated aliphatic hydrocarbons such as chloroform, dichloromethane, methyl octoxide or carbon tetrachloride, carried out Particularly preferred solvents are water, acetic acid and carbon tetrachloride. If the oxidation occurs immediately after the halogenation and without separation of the halophenol is carried out, carbon tetrachloride is a particularly preferred solvent, because it can be easily separated again

The examples and the comparative example illustrate the invention.

example 1

(A) 136 g (1 mol) of 23,6-trimethylphenol are dissolved in 1000 g of acetic acid. Be in solution during One hour at room temperature 75 g (1.06MoI) of chlorine gas introduced. When the addition is complete, in nitrogen was passed into the reaction mixture in order to remove the hydrogen chloride formed. Thereafter the acetic acid is distilled off. Yield 169.8g

from a melting point of 794 to 804 ^° C. The product is identified by elemental analysis, IR and NMR spectrum

(B) 17.0 g (Q ₁ I mol) of the 2A6-trimethyl-4-chlorophenol obtained in (A) are dispersed in 40 ml of water and 10 g of concentrated nitric acid are added dropwise within 30 minutes while stirring vigorously Reaction, and a yellowish brown oil is formed, which is dispersed in water.After stirring for a further 30 minutes, the reaction mixture is steam distilled.As soon as the yellow color of the distillate has disappeared, the steam distillation is stopped and the distillate is extracted with ether.The ether extract is washed with aqueous sodium bicarbonate solution , dried over sodium sulfate and evaporated. Yield: 13.6 g (90.6% of theory), 23,6-trimethyl-p-benzoquinone.

Example 2

According to the example ', but using> o 17.0 g (0.1 mol) 2.34V trimethyl-4-chlorophenol according to Example 1 (A) was prepared, instead of 23.6-trimethyl-4-chlorophenol, 13.2 g (88% of Theory) obtained 234-trimethyl-p-benzoquinone.

Example 3

The oxidation is with 17.0 g (0.1 mol) of the in Example 1 (A) obtained 23,6-trimethyl-4-chlorophenol The amount of the solution containing 10 g of nitric acid is changed. The results are in jn Table I summarized

Table I.
Ml water):

10 20 60

40

Yield,% of theory: 90 88 92 92

From Table I it can be seen that using different concentrations of nitric acid is practical no change in yield occurs.

Example 4

17.0 g (0.1 mol) of the 23,6-trimelhyl-4-chlorophenol obtained according to Example 1 (A) are oxidized with a solution of 15 g of chromic acid in 20 g of acetic acid, γ worked up yield 12.6 g (84% of theory) 2,3,6-trimelhyl-pbenzoquinone.

Example5

17.0 g (0.1 mol) of the 23,6-trimethyl-4-chlorophynol prepared according to Example 1 (A) are dissolved in 100 g of acetic acid dissolved and within 30 minutes while stirring dropwise with 10 g of concentrated nitric acid offset The reaction starts immediately. After stirring for an additional 30 minutes, the reaction mixture becomes steam distilled and worked up according to Example 1. Yield 13.8 g (92% of theory) 2,3,6-trimethyl-p-befiZochtnon.

Example 6

17.0 g (0.1 mol) of the 2,3,6-trimethyl-4-chlorophenol prepared according to Example 1 (A) are dissolved in 50 g of carbon tetrachloride and within 30 minutes with vigorous stirring at 40 "C with a mixture of 10 g of technical, 64 percent strength by weight nitric acid and 20 ml of water are added. When the addition is complete, the mixture is stirred for a further 30 minutes. The carbon tetrachloride solution is then separated off and evaporated % cLTh.) Trimethylbenzoquinone contains The residue is fractionally distilled. ^Bp . 5 9arc (3 Torr), yield 14.0 g of almost pure 2A6-trimethylp-benzoquinone,

Example 7

(A) 136 g (1 mol) 2A6-TrimetbylphenoI are dissolved in 900 g of acetic acid and within an hour with a solution of 160 g (1 mol) of bromine in 100 g of acetic acid is added. The reaction is carried out at room temperature carried out With dropwise addition the color of the bromine disappears immediately and the The reaction starts immediately. When the addition is complete, the hydrogen bromide formed is removed by passing in Removed nitrogen. 23,6-Trimethyl-4-bromophenol is obtained in quantitative yield with a melting point of 91-92 ° C

(B) 214 g (0.1 mol) of the 23,6-trimethyl-4-bromophenol obtained in (A) are dissolved in 100 g of acetic acid dissolved and mixed with 10 g of concentrated satpitric acid within 30 minutes with stirring. The reaction starts immediately. After stirring for a further 30 minutes, the reaction mixture is steam distilled and worked up as in Example 1 (B), yield 12.0 g (80.0% of theory) of 23,6-trimethyl-p-benzoquinone.

Example 8

13.6 g (0.1 mol) of 2 _t 3.'ö-trimethylphenol were dissolved in 100 g of acetic acid in the solution can be introduced at 20 to 30 ⁰ C under stirring 7.4 g (0.104 MoI) of chlorine gas Gas chromatographic analysis of Product shows that the p-chlorine derivative has formed almost quantitatively. Then, without separating off the acetic acid, 10 g of technical, 63% nitric acid are added dropwise to the reaction mixture within 30 minutes Stirred for 30 minutes and then steam distillation The steam distillation is stopped when the yellow color of the distillate has disappeared, the distillate is then extracted with ether The ether extract is washed with aqueous sodium bicarbonate solution, dried over sodium sulphate and evaporated. ) 23.6-trimethyl-pbenzoquinone.

Example 9

According to Example 8, 2,34-trimethylphenol is reacted. Yield 13.2 g (88% of theory) of 2,34-trimethyl-pbenzoquinone.

Example 10

The halogenation and the subsequent oxidation are carried out according to Example 8, but the Solution of the 2,3,6-trimethylphenol in acetic acid in the chlorination 0.068 g of iodine added. Yield 14.2 g (94.7% of theory) 2,3,6-trimethyl-p-benzoquinone.

Example 11

The chlorination is carried out according to Example 8, but the chlorination product with a solution of 15 g chromic acid oxidized in 20 g acetic acid. After working up according to Example 1, 12.6 g (84% d. Th.) 2,3,6-trimethyl-p-benzoquinone obtained.

Example 12

A 5 | four-necked flask with a stirrer, a reflux condenser, a chlorine inlet pipe and a thermometer, 1000 g carbon tetrachloride and 408 g (3 mol) 2,3,6-TrimethyIphenol are then charged into the Solution within 2 hours at 40 ° C 210 g (3 mol) of chlorine gas are introduced immediately thereafter, for two hours at 40 ° C., a mixture of 210 g of technical, 63% by weight Nitric acid and 600 g of water added dropwise. After the addition is complete, the mixture becomes another Stirred for an hour then left to stand, the lower carbon tetrachloride layer separated with water washed and evaporated. 460 g of a red oil remain, which contains 405 g (90% of theory) of 2,3,6-trimethyl-pbenzoquinone contains

Example 13

According to Example 3, but using 2,3,5-trimethylphenol instead of 2,3,6-T / imethylphenol, the 23,5-trimethyl-p-benzoquinone is obtained in 85 percent yield.

Example 14

According to Example 12, but with the addition of 2 g of iodine to the carbon tetrachloride solution of 23,6-trimethylphenol, 475 g of distillation residue are obtained, which contains 428 g (95% d, Th,) 2 ^, 6-trimethyl-p-benzene; rachinone

Example 15

The procedure is as in Example 8, but used

instead of 10 g of 63 percent nitric acid 50 g a 10 percent hydrogen peroxide solution. 133 g (88 percent of theory) of 2 ^, 6-trimethyl-p-benzoquinone are obtained.

Example 16

The halogenation and subsequent oxidation is carried out according to Example 8, with the modification that 15.8 g of potassium permanganate in 100 g of acetic acid are used instead of nitric acid. This gives 13.8 g (91 percent of theory) of 23,6-trimethyl-p-benzoquinone.

Comparative example

17.0 g (0.1 mol) of the of Example 1 (A) obtained 2 ^, 6-trimethyl-4-ehIorphenoIs be dispersed Thereafter, in 40 ml of water in the mixture for 3 hours at 60 to 80 ⁰ C and air was passed in with vigorous stirring. However, there was no oxidation reaction and the starting compound was recovered almost quantitatively.

Claims (1)

Claim; Process for the preparation of trimethyl-p-benzoquinones by oxidation of trimethyl-p-halophenols, characterized in that the oxidizing agent used is chromic acid, permanganic acid, a peroxide, diluted, concentrated or fuming nitric acid is used